The present invention is directed to the improved gellation of hydrocarbons liquids for a variety of applications. The present invention is specifically directed to an enhancer for improving the gelling of hydrocarbon liquids when treated with phosphate esters and crosslinking agents.
In order to maximize the amount of oil derived from an oil well a process known as hydraulic pressure stimulation or, more commonly, formation fracturing is often employed. In formation fracturing, fluid is pumped under high pressure down the wellbore through a steel pipe having small perforations in order to create or perpetuate cracks in the adjacent subterranean rock formation. The fluid employed must be able to withstand exceptionally high shear forces. Gelled liquids, and particularly gelled hydrocarbons, are well-suited for this application. The fracturing fluid has entrained therein a particulate material called a proppant (e.g., sand or other particulate matter). The proppant particles become wedged in the cracks of the formation to keep the cracks open once the external pressure is released, thereby enabling continued production stimulation of the well. It is ideal from the vantage points of time economy and cost-savings to have the gelling of the hydrocarbon take place more or less continuously on-site or xe2x80x9con the flyxe2x80x9d as the components are brought together as they are pumped down the well bore. Accordingly, it is both desirable and adavatageous that gellation occur as quickly as possible.
The viscosity of the hydrocarbon gel is important for proppant transport. Poor gel viscosity can lead to a phenomenon known as xe2x80x9cscreening outxe2x80x9d, whereby the gel is not sufficiently capable of suspending the proppant. Large quantities of proppant material, upwards of 3 to 15 pounds of sand per gallon of pumping fluid, can settle out inside the well bore, as well as in the fracture. If the proppant has dropped, or screened out, part of the created fracture is effectively closed when the external pressure is released. When screening out occurs, the fracturing process must be interrupted and the well bore cleaned out, costing both significant time and expense.
Rapid gellation of hydrocarbon liquids is also beneficial when tanks or vessels carrying such liquids are damaged during transport and cause highly hazardous and environmentally damaging spillage. A fast gelling additive composition that can be added to the leaking volume of hydrocarbon liquid would serve to prevent or, at least, reduce or contain the spillage and the resultant damage. A variety of other applications exist which require the rapid gellation of hydrocarbon liquids, and to which the present invention would apply.
Several means for gelling hydrocarbon liquids are disclosed in the prior art. U.S. Pat. No. 5,417,287 to Smith et al. is directed to a method for fracturing a subterranean formation which involves adding to a hydrocarbon liquid (a) an organic phosphate of the formula HPO4RRxe2x80x2 where R is an alkyl or alkaryl group having from 6 to 18 carbon atoms and Rxe2x80x2 is hydrogen or an aryl, alkaryl or alkyl group having from 1 to 18 carbon atoms; and (b) a ferric salt.
Smith et al U.S. Pat. No. 5,614,010 teaches gelling agents suitable for use in methods of fracturing formations, comprising ferric salts, certain phosphate esters, a low molecular weight amine such as triethanolamine or triethylamine, and an optional surfactant. Smith ""010, however, does not achieve, e.g., the impressive hydrocarbon viscosities achievable by the present methods and compositions, and moreover Smith uses twice as much phosphate ester and ferric ion as required herein.
Smith et al U.S. Pat. No. 5,647,900 discloses gelling agents for hydrocarbon gels comprising combinations of certain orthophosphate esters and a composition comprising a source of ferric ions, a C2-C12 amine, and a polycarboxylic acid or salt thereof. However, the gels formed in the Smith et al inventions demonstrate lower (Marsh funnel) viscosities than those achieved by the gels of the present invention. Moreover, the Smith et al gels are formed using twice as much phosphate ester and ferric ion (1% of each relative to the volume of liquid hydrocarbon to be is gelled) as compared to the invention as demonstrated, e.g., in the Examples of the invention.
European Patent Application No. 551021A1 to McCabe et al. is directed to gelling a hydrocarbon liquid by adding thereto an at least partially neutralized alkyl orthophosphate acid ester, a C8--C18 surface active amine and C2-C4 monohydric alcohol. The surface active amine employed includes alkyl and alkanol amines having from about 8-18 carbon atoms, N-heterocyclic amines, alkyl substituted derivatives of such heterocyclics and mixtures thereof. Amines having more than one nitrogen group are preferred and imidazoline, such as that prepared from the reaction of a tall oil fatty acid with diethylenetriamine, is most preferred.
U.S. Pat. No. 4,316,810 to Burnham is directed to a fracturing composition which is an aluminum salt of an oxaalkyl phosphate in an oil base liquid. Surface active agents are not disclosed.
U.S. Pat. No. 4,153,649 to Griffin is directed to the reaction product of a hydroxy ether and a pentavalent phosphorus compound and an alcohol. The hydroxy ether has the formula ROR1OH wherein R is a C1 to C6 alkyl group, R1 Is a C2 or C3 alkylene group and the total carbon atoms of R1 and R range from 3 to about 8. The disclosed reaction product may be employed in the gelling of hydrocarbon liquids when used with a compound containing a multivalent metal cation.
U. S. Pat. No. 5,271,464 to McCabe is directed to a method of plugging or sealing a subterranean formation by introducing a rapidly gelling hydrocarbon thereto. To the hydrocarbon is added a first component which is an at least partially neutralized alkyl orthophosphate ester and a second component which is the reaction product of an aqueous source of aluminum or ferric ions and a C8-C18 surface active amine in the presence of a water miscible organic solvent. The surface active amine is as defined above for European Patent Application No. 551021A1, also to McCabe. The water miscible organic solvent is generally a monohydric alcohol.
U.S. Pat. No. 3,494,949 to Monroe et al. is directed to an additive for improving the viscosity of motor oils which is generally an aluminum salt of an alkyl orthophosphate.
U.S. Pat. No. 2,983,678 to Pellegrini et al. is directed to an additive for lubricating oils which is generally a rare earth metal salt of a diester phosphate.
U.S. Pat. Nos. 4,877,894, 5,057,233, 5,110,485, and 5,202,035 to Huddleston are related to phosphate esters as hydrocarbon gelling agents. The gelling agent is generally formed by first reacting phosphorus pentoxide with triethyl phosphate, followed by reaction with a mixed alcohol that may have a substantial hexanol component. The gelling agent may also be in the form of an aluminum salt, by reaction of the phosphate ester with aluminum sulfate in the presence of solvent. None of the gelling agents or systems of the Huddleston patents appreciate the benefit of adding an amine, e.g., oxyalkylated amine, or an amine blend enhancer in the gelling of liquid hydrocarbons. The Huddleston teachings are also devoid of appreciation of the benefits obtained by using a ferric salt.
U.S. Pat. No. 5,190,675 and EP 225,661 to Gross (Dowell Schlumberger) employ metal phosphate diesters in the gelling of liquid hydrocarbons. The metal phosphate diester is prepared by reacting a phosphorus pentoxide with a triethyl phosphate , followed by reaction with an alcohol to form the diester. The metal salt is formed in the presence of the hydrocarbon to be gelled by the addition of a non-aqueous source of aluminum, e.g., aluminum isopropoxide. The gelling agents of Gross are devoid of the presence of an amine enhancer and a crosslinking ferric salt, and accordingly, Gross"" methods do not achieve the level of beneficial gelling properties achievable by the present invention.
While a variety of systems are available for gelling hydrocarbon liquids for the application discussed above, there exists a clear need in the art for a means of improving the known systems to achieve decreased gelling times and improved viscosity.
Therefore, it is one object of the present invention to provide such a means for improving known gellation systems.
It is a further object of the present invention to provide a novel gellation system exhibiting decreased gelling times and improved viscosity.
It is yet another object of the present invention to provide a composition for decreasing gelling time and improving viscosity for use in conventional methods of gelling hydrocarbon liquids.
These as well as other objects are achieved by providing a composition for improving the gelling of hydrocarbon liquids, which composition comprises an enhancer chosen from a specific class of amines, a certain class of phosphate esters, and a crosslinking agent.
Such objects are also achieved by providing a method of gelling hydrocarbon liquids which involves adding to a hydrocarbon liquid the enhancer, the phosphate ester, and the crosslinking agent.
A further object of the invention is to provide synergistic combinations of enhancers, as well as synergistic phosphate ester combinations, useful in improving the gelling of hydrocarbon liquids.
More particularly, the objects of the invention are achieved by providing a method of gelling hydrocarbon liquids which involves adding to a hydrocarbon liquid (a) a phosphate ester or a mixture of phosphate esters; (b) a crosslinking , agent; and (c) an amine enhancer which is a C2-C22 amine, a C2-C22 oxyalkylated amine, or mixtures thereof.
The present invention is drawn, in part, to an enhancer for use in the gelling of hydrocarbon liquids when such a liquid is treated with a phosphate ester and a crosslinking agent. The invention is also directed to novel compositions comprising the enhancer, a phosphate ester (chosen from a specified class and to be described more fully below), and the crosslinking agent. The invention relates further still to gel compositions which results from adding to a hydrocarbon liquid the enhancer, the phosphate ester, and the crosslinking agent.
Hydrocarbon liquids which are appropriate for use in accordance with the present invention include kerosene, diesel oil and crude oil, gasoline and other aliphatic and aromatic hydrocarbons such as octane, heptane, paraffinic oils and lubricating oils. The choice of the liquid for use in accordance with the present invention will depend on the particular industrial or chemical application. In industrial applications, diesel oil is typically gelled, however other liquid hydrocarbons are also well-suited for use in the present invention. Other factors, such as accessibility and economics(cost) of liquid hydrocarbons at a particular site, dictate to a degree the choice of hydrocarbon to be gelled.
The crosslinking agent or activator employed in the practice of the invention is a salt of a multivalent cation, and is preferably the salt of a multivalent metal cation. Although a wide variety of metal salts, such as aluminum salts and rare earth metal salts, are within the scope of the present invention, ferric salts are generally preferred. Preferred ferric salts include ferric nitrate and ferric sulfate.
The phosphate ester component of the present invention can be the reaction product of a pentavalent phosphorus compound and an alcohol, and their preparation is according to well-known synthesis procedures (see, for example, Crawford et al U.S. Pat. No. 3,757,864, Poklacki U.S. Pat. No. 4,007,128, and Burnham et al U.S. Pat. No. 4,200,539, all of which are incorporated herein by reference). More preferably, the phosphate esters useful herein are the reaction product of 1) pentavalent phosphorus (e.g., P2O5) reacted with a trialkylphosphate, and 2) at least one alcohol. The synthesis of these phosphate esters takes place according to well-known procedure, for example, as set forth in Huddleston U.S. Pat. No. 5,202,035 (incorporated herein by reference). Alternatively, the phosphate esters useful in the present invention can be prepared by transesterification of orthophosphate ester with triethyl phosphate, for example, Jones et al U.S. Pat. No. 5,649,596.
More preferably, the phosphate ester is formed from P2O5 and a tri-loweralkyl phosphate when reacted with a mixture of alcohols and/or oxyalkylated alcohols yielding phosphate monoesters, symmetric diesters, asymmetric diesters, symmetric triesters, asymmetric triesters, and mixtures of any of these. xe2x80x9cTri-loweralkyl phosphatexe2x80x9d in the present context is to be understood as meaning tri -C1-C6 alkylphosphate. The alcohols suitable for reaction with the phosphate intermediate include alkyl alcohols, aralkyl alcohols, ether-containing alkyl alcohols, and aralkyl ether alcohols (or oxyalkylated aralkyl alcohols), and mixtures thereof. It is to be understood that the term xe2x80x9calkylxe2x80x9d as it applies to the present phosphate esters includes straight and branched alkyl groups. xe2x80x9cArylxe2x80x9d includes C6 to C12 aryl. Therefore, when ether alcohols are employed one or more oxyalkene groups such as oxyethylene, oxypropylene or oxybutylene is present in the xe2x80x9cRxe2x80x9d group of the alcohol designated as ROH. Accordingly, the phosphate ester that is formed is an ether phosphate ester. Thus, the term xe2x80x9cphosphate estersxe2x80x9d as used herein includes ether phosphate esters. The phosphate esters of the present invention will thus be mixtures of esters conforming to the following structures: 
wherein R, R1, and R2 are independently C1-C18 alkyl, C6 aryl, C1-C18 alkyl or di C1-C18 alkyl C6 aryl, C1-C18 alkyl ether, C6 aryl ether, or C1-C18 alkyl or di C1-C18 alkyl C6 aryl ether, and where any ether linkage has the following structure:
xe2x80x94O(CH2xe2x80x94CHRxe2x80x2)xe2x80x94
wherein Rxe2x80x2 is hydrogen, methyl or ethyl.
More preferably, the phosphate ester according to the invention is a mixture of mixed esters such as asymmetric phosphate diesters (i.e., where R≈R1). The ability to obtain particularly useful phosphate ester mixtures within the scope of the invention hinges upon the specific alkyl, alkaryl, alkyl ether,alkaryl ether, aralkyl, and/or aralkyl ether moieties in the alcohol reactants. For example, a phosphate ester mixture that contains a distribution of C2, C8, C10, and oxyalkylated C6 aryl groups is particularly useful herein.
The phosphate ester of the present invention is preferably non-neutralized. However, depending on the particular enhancer employed, it is also within the scope of the invention to at least partially neutralize the phosphate ester.
The enhancer of the present invention is an amine, a mixture of amines, or an amine and another non-amine compound that functions as an enhancer. The following amine structures are within the scope of the enhancer of the present invention: 
where R, R1, and R2 are independently hydrogen, C1-C18 alkyl, C5-C6 cycloalkyl, aryl, C1-C18 substituted aryl, or
xe2x80x94(CH Rxe2x80x2xe2x80x94CHO)n
wherein Rxe2x80x2 is hydrogen, methyl or ethyl, n is an integer from 1 to 100, and wherein the O atom of the terminal or xe2x80x9cnthxe2x80x9d xe2x80x94(CH Rxe2x80x2xe2x80x94CHO)n group is bound to a hydrogen atom; 
where R is hydrogen, C1-C18 alkyl, or a group of the structure
xe2x80x94(CH Rxe2x80x2xe2x80x94CHO)nxe2x80x94
wherein Rxe2x80x2 is hydrogen, methyl or ethyl, n is an integer from 1 to 100, and wherein the O atom of the terminal or xe2x80x9cnthxe2x80x9d xe2x80x94(CH Rxe2x80x2xe2x80x94CHO)n group is bound to a hydrogen atom; R1 is hydrogen, C1 alkyl or a group of the structure
xe2x80x94(CH Rxe2x80x2xe2x80x94CHO)nxe2x80x94
wherein Rxe2x80x2 is hydrogen, methyl or ethyl, n is an integer from 1 to 100, and wherein the O atom of the terminal or xe2x80x9cnthxe2x80x9d xe2x80x94(CH Rxe2x80x2xe2x80x94CHO)n group is bound to a hydrogen atom; R2 is hydrogen or
xe2x80x94(CH Rxe2x80x2xe2x80x94CHO)nxe2x80x94
wherein Rxe2x80x2 is hydrogen, methyl or ethyl, n is an integer from 1 to 100, and wherein the O atom of the terminal or xe2x80x9cnthxe2x80x9d xe2x80x94(CH Rxe2x80x2xe2x80x94CHO)n group is bound to a hydrogen atom; and R3 is a C2 or C3 alkyl; or 
where R is C6-C18 alkyl, R1 is hydrogen or a group of the structure
xe2x80x83xe2x80x94(CH Rxe2x80x2xe2x80x94CHO)nxe2x80x94
wherein Rxe2x80x2 and n are as defined above with respect to the diamine; and R2 is a C3 alkyl. With regard to amine structures shown above, the substituent group xe2x80x9calkylxe2x80x9d or xe2x80x9caralkylxe2x80x9d has the meaning of both straight and branched alkyl groups.
More preferably, the amine enhancer an oxyalkylated amine. Thus, preferred oxyalkylated amines include oxyalkylated alkyl amines such as ethoxylated alkyl amines having from 1 to about 100 moles of ethylene oxide per mole of amine and ethoxylated alkyl amines having from about 1 to about 18 carbon atoms in the alkyl group; polyoxypropylene alkyl amine having from 1 to about 100 moles of propylene oxide per mole of amine; and polyoxybutylene alkyl amine having 1 to about 100 moles of butylene oxide per mole of amine. The term xe2x80x9coxyalkylated alkyl aminesxe2x80x9d also encompasses oxyalkylated dialkyl amines, such as ethoxylated di C2-C8 alkyl amines having from 1 to about 100 moles of ethylene oxide per mole of amine; polyoxypropylene dialkyl amine having from about 1 to about 100 moles of propylene oxide per mole of amine, and polyoxybutylene dialkyl amine having from about 1 to about 100 moles of butylene oxide per mole of amine. More preferably, the term xe2x80x9coxyalkylated aminesxe2x80x9d means oxyalkylated diamines and oxyalkylated C6 aryl amines. A particularly preferred oxyalkylated amine is N,N-di n-butyl ethanol amine, having the following structure 
The amount of enhancer to be employed in the present compositions and methods is an amount effective to increase the rate of gel formation and to increase the viscosity thereof, relative to known gelling systems that do not incorporate an enhancer of the present invention. In general, an effective amount of amine enhancer is from 0.01% to 5.0% relative to the volume of liquid hydrocarbon to be gelled. More preferably, 0.1% to 0.5% of amine enhancer is employed.
Enhancer blends or mixtures are also appropriate for use in the present invention. Preferred blends include at least one oxyalkylated amine as set forth above with another to enhancer component which is either an amine, a non-nitrogen containing compound, a quaternary nitrogen compound or an amide. It should be noted that blends containing more than two components are also within the scope of the present invention.
When a second enhancer component is another amine, this second amine may be chosen from oxyalkylated amines, such as those set forth above, or alkyl amines such as C2-C22 alkyl amines, C2-C22 dialkyl amines, C2-C22 alkyl diamines, C2-C22 dialkyl diamines, C2-C22 dialkyl amino C2-C22 alkylamines, and analogs of these compounds having one or more carbon-carbon double bonds in the alkyl moiety. xe2x80x9cAlkylxe2x80x9d within the context of, e.g., alkylamine, is to be understood as meaning straight and branched alkyl groups. The term xe2x80x9cC2-C22 dialkylxe2x80x9d is intended to mean that each alkyl group can be from C2-C22. A preferred class of alkyl amines to be used in conjunction with an oxyalkylated amine are fatty amines, and particularly unsaturated fatty amines, such as mono- and di-oleyl amines.
Non-nitrogen containing components which are appropriate in the enhancer blend include oxyalkylated glycerides, oxyalkylated mono- and di-esters and oxyalkylated alcohols and phenols, as well as non-oxyalkylated alcohols and phenols, a fatty acid, or a mixture of a fatty acid and a glyceride.
The specific proportion or ratio of enhancer components varies depending on the nature of the individual enhancer components, as well as on the particular application requiring the gelling of liquid hydrocarbon. However, in general, when the enhancer is a blend comprising at least one oxyalkylated amine and another enhancer component, the components may be mixed at a ratio from about 9:1 to 1:9 oxyalkylated amine to other enhancer component. When it is advantageous that the enhancer be a mixture or blend of at least one oxyalkylated amine (A) and two other enhancer components (e.g., a second amine enhancer compound (B) and a non-nitrogen-containing enhancer compound (C)), the mixing ratio is from about 1:1:1 to 6:3:1 of A:B:C. Further, depending on the particular industrial application, it is within the scope of the invention to employ enhancer blends having, for example, four, five, or more enhancer components. When this is the case, the ratios of the individual components can be determined by the skilled practitioner without resort to undue experimentation.
The invention is further directed to a gel-forming hydrocarbon composition for fracturing formations comprising: 1) a hydrocarbon liquid capable of gellation, 2) 0.01 to 10.0% by weight of a phosphate ester which is a reaction product comprising either A) phosphorus pentoxide reacted with a tri-loweralkyl phosphate and subsequently reacted with either an alcohol, an oxyalkylated alcohol or mixtures thereof or B) phosphorous pentoxide reacted with either an alcohol, an oxyalkylated alcohol or mixtures thereof to form a phosphate ester or mixed phosphate ester which is subsequently reacted with a tri-loweralkyl phosphate, 3) a crosslinking agent in an amount effective to gel said hydrocarbon liquid, 4) from about 0.085 molar equivalent to about 0.31 molar equivalent of the phosphate ester of an enhancer comprising an amine selected from the group consisting of alkyl amines, oxyalkylated amines, and mixtures thereof, and 5) optionally a surfactant.
As demonstrated by several of the examples that follow, the invention includes novel synergistic combinations of enhancer components, as well as synergistic phosphate ester combinations. More specifically, the viscosities obtained (as indicated in centipoises and Marsh Funnel time (minutes)) for the present hydrocarbon gel systems using mixtures of enhancer components or mixtures of phosphate esters are greater than the viscosities of the individual components when used at comprable volumes. For example, in Table II below it will be seen that all of the enhancer mixtures have a synergistic effect on production of gels of very high viscosity (in centipoises), relative to the same volume of each of the enhancer components individually.
Particularly preferred synergistic enhancer combinations include, but are not limited to, an ethoxylated di-C4 alkyl amine having one mole of oxyethylene per mole of amine in combination with any of the following oxyalkylated amines: an ethoxylated C16-C18 alkyl amine having two moles of oxyethylene per mole of amine; an ethoxylated C8-C16 alkyl amine having two moles of oxyethylene per mole of amine; an ethoxylated C18 alkenyl amine having two moles of oxyethylene per mole of amine; an ethoxylated C16-C18 alkenyl amine having two moles of oxyethylene per mole of amine. Synergistic combinations of any of the following enhancer amines are also preferred: an ethoxylated C16-C18 alkyl amine having two moles of oxyethylene per mole of amine; an ethoxylated di-C1 alkyl amine having one mole of oxyethylene per mole of amine; an ethoxylated di-C2 alkyl amine having one mole of oxyethylene per mole of amine; triethanolamine; and an ethoxylated C8-C16 alkyl amine having two moles of oxyethylene per mole of amine.
Mixtures of phosphate esters in accordance with the invention also have a synergistic effect on gel viscosity. This feature of the invention is exemplified in Table III below. Various combinations of the following phosphate esters are effective in this particular aspect of the invention: a C2, C8, C10 alkyl phosphate, having 30.3% C2, 32.1% C8, and 37.6% C10; a C2-C18 alkyl, C1-C18 alkyl ether phosphate having 30.2% C2, 30.3% C8, 35.6% C10, and 3.9% C1 alkyl ether oxyalkylated with 1 mole of oxypropylene; a C2-C18 alkyl, C1-C18 alkyl ether phosphate having 29.7% C2, 26.3% C8, 30.8% C10, and 13.2% C6 alkyl ether oxyalkylated with 1.5 mole of oxyethylene; a C2-C18 alkyl, C1-C18 alkyl ether phosphate having 30.3% C2, 4.5% C4, 23.8% C8, 27.9% C10, and 13.5% C6 alkyl ether oxyalkylated with 1.5 moles of oxyethylene; a C2-C18 alkyl, C1-C18 alkyl ether phosphate having 27.4% C2, 24.1% C8, 28.4% C10, and 20.1% C8-C10 alkyl ether oxyalkylated with 3 moles of oxyethylene; a C2-C18 alkyl, C1-C18 alkyl ether phosphate having 25.7% C2, 22.7% C8, 26.7% C10, and 24.9% C8-C10 alkyl ether oxyalkylated with 5 moles of oxyethylene; a C2-C18 alkyl, C1-C18 alkyl ether phosphate having 25.4% C2, 22.1% C8, 26.2% C10, and 26.3% C16-C18 alkyl ether oxyalkylated with 3 moles of oxyethylene; a C2-C18alkyl, C6aryl ether phosphate having 31% C2, 25% C8, 30% C10, and 14% C6 aryl ether oxyalkylated with 1 mole of oxyethylene; a C2-C18 alkyl, C6 aryl ether phosphate having 30.6% C2, 21.6% C8, 25.4% C10, and 22.4% C6 aryl ether oxyalkylated with 1 mole of oxyethylene; a C2-C18 alkyl, C6 aryl ether phosphate having 25.9% C2, 22.8% C8, 26.8% C10, and 24.5% C6 aryl ether oxyalkylated with 6 moles of oxyethylene; a C2-C18 alkyl, C6 aryl ether phosphate having 23.8% C2, 21.0% C8, 24.6% C10, and 30.6% C6 aryl ether oxyalkylated with 9 moles of oxyethylene; a C2-C18 alkyl, C6 aryl ether phosphate having 26.2% C2, 25.5% C8, 29.9% C10, and 18.5% aryl ether oxyalkylated with 10 moles of oxyethylene; a C2-C18 alkyl, C6 aryl ether phosphate having 29.8% C2, 26.3% C8, 30.9% C10, and 13.0% C6 aryl ether oxyalkylated with 1 mole of oxybutylene; a C2-C18 alkyl, C1-C12 alkyl or dialkyl C6 aryl ether phosphate having 25.2% C2, 22.3% C8, 26.1% C10, and 26.4% C9 alkyl C6 aryl ether oxyalkylated with 4 moles of oxyethylene; and a C2-C18 alkyl, C1-C18 alkyl ether, C6 aryl ether phosphate having 25.9% C2, 64.7% C8-C10 alkyl ether oxyalkylated with 1 mole of oxyethylene, and 9.4% C6 aryl ether oxyalkylated with 1 mole of oxyethylene. Particularly preferred phosphates ester combinations are a C2, C8, C10 alkyl phosphate, having 30.3% C2, 32.1% C8, and 37.6% C10 with a C2-C18 alkyl, C6 aryl ether phosphate having 30.6% C2, 21.6% C8, 25.4% C10, and 22.4% C6 aryl ether oxyalkylated with 1 mole of oxyethylene; a C2-C18 alkyl, C6 aryl ether phosphate having 31% C2, 25% C8, 30% C10, and 14% C6 aryl ether oxyalkylated with 1 mole of oxyethylene with a C2-C18 alkyl, C6 aryl ether phosphate having 29.8% C2, 26.3% C8, 30.9% C10, and 13.0% C6 aryl ether oxyalkylated with 1 mole of oxybutylene; a C2, C8, C10 alkyl phosphate, having 30.3% C2, 32.1% C8, and 37.6% C10 with a C2-C18alkyl, C6aryl ether phosphate having 31% C2, 25% C8, 30% C10, and 14% C6 aryl ether oxyalkylated with 1 mole of oxyethylene. Especially preferred is the combination of a C2, C8 C10 alkyl phosphate, having 30.3% C2, 32.1% C8, and 37.6% C10 with a C2-C18 alkyl, C6 aryl ether phosphate having 30.6% C2, 21.6% C8, 25.4% C10, and 22.4% C6 aryl ether oxyalkylated with 1 mole of oxyethylene.